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Status Report, Vol. 49, No. 4 | May 29, 2014 Subscribe

Side airbag benefits extend to people in rollover crashes

The side curtain airbag and driver airbag deploy in the Hyundai Genesis during an IIHS side test. The car's side curtain airbags also are designed to deploy in a rollover crash.

Side curtain airbags that deploy in rollover crashes help reduce front-seat occupant deaths in first-event rollovers by 41 percent, the National Highway Traffic Safety Administration (NHTSA) estimates in a preliminary look at the benefits of this relatively new type of airbag. In the report, the agency also updates estimated benefits for four other types of side airbags, adding to the evidence that they are saving lives and reducing injuries.

Curtain airbags designed to deploy in rollovers and remain inflated longer began to appear in 2002 models, and by the 2014 model year about 38 percent of new passenger vehicles had them. These rollover airbags are expected to become the norm as manufacturers work to meet a new ejection mitigation standard that began phasing in with 2014 models (see "New ejection rule may spur changes in side airbags," April 26, 2011).

Other types of side airbags have been available on U.S. passenger vehicles since 1996. These include curtain airbags designed to deploy from the roof or door in side crashes; torso airbags, which deploy from the seat; combination head/torso airbags; and curtain plus torso airbags. Curtain plus torso airbags are the most common, found in 83 percent of 2014 models, HLDI estimates.

Based on analysis of data from the Fatality Analysis Reporting System, NHTSA estimates that curtain plus torso airbags reduce the risk of a driver or right front-seat passenger dying in a near-side crash by 31 percent, and combination head/torso airbags reduce the risk by 25 percent. Curtain airbags alone lower the risk by 16 percent, while torso airbags trim the risk by 8 percent. The agency's estimated benefits of side airbags are in line with earlier research by the Institute and other groups (see "Surviving side crashes: Side airbags are reducing driver deaths," Oct. 7, 2006, and "Combination side airbags reduce death and injury risk," Dec. 20, 2012).

In side-impact crashes, the side structure of the struck vehicle or the structure of the striking vehicle can injure even properly belted occupants. In some cases, occupants collide with nearby objects, such as utility poles. Side airbags cushion and spread the load of these impacts to prevent any part of an occupant's body from sustaining concentrated impact forces. Side airbags that offer head protection are particularly important because they may be the only thing between a person's head and the front of a striking vehicle, a tree or other object, or the ground in the event of a rollover.

All of the vehicles that earn good ratings in the Institute's crash test assessing occupant protection in side impacts have head-protecting side airbags. These vehicles also have side structures that resist major intrusion into the occupant compartment. NHTSA doesn't mandate side airbags specifically but does require a high level of head and torso protection for occupants in side crashes.

Vehicles roll over in less than 3 percent of all crashes, but these crashes account for more than a third of passenger vehicle occupant deaths. When vehicles do roll, side curtain airbags can prevent an occupant's head and upper body from contacting the ground and also keep unbelted people inside the vehicle. In addition, safety belts hold occupants in their seats and inside the vehicle when people use them, while strong roofs that resist occupant compartment intrusion reduce the risk of serious injury and death.

NHTSA notes that its preliminary estimate of the benefits of curtain airbags that deploy in rollovers is based on limited data of the fatal crash experience of 2011 and earlier model vehicles. This type of airbag didn't begin to see rapid growth in installations until the 2010 model year.

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